Historically, countries ruled by monarchs dictated that the religion of choice was the same as that of the monarch – Anglo-Saxon kingdoms became christian when the king did. Nobody had a choice; at least openly (you do have to suspect that paganism might have officially died out when the king switched, but it may have taken longer in the backwoods where the banjos are played).
In fact it could be worse – the christianisation of the Isle of Wight occurred when a pogrom of all the pagan believers was enacted.
This didn’t please the non-conformists of England during the 16thC and resulted in a number of religious colonies in what would become the USA. Of course not all of the colonialists were non-conformists, but they had better conform to whatever non-conformists were in charge of their relevant colony!
Religious conflict was almost inevitable – both in Europe (although some of these ‘religious wars’ were arguably and to a greater or lesser extent political in nature) and in the colonies that would later become US states. For example, Maryland had a time of Plundering, and there were the Salem witchcraft “trials” plus a whole lot of individual level persecution (just ask early Quakers).
So history tells us that an established church has a history of repressing religious minorities. Sometimes in terms of a lack of rights (such as the prohibition of catholics holding public office in England before the 1829 act), forced to pay a “church tax” to the established church (such as the church tax in Denmark), or violent measures.
And lastly, and probably most importantly, everyone in favour of some form of theocracy is somehow under the belief that it will be their church that is favoured. It won’t be of course because there are so many different choices that somebody will be disappointed.
And for the record, I fully support the establishment of the Satanic Temple.
